Acoustic fields can be applied to fluids (e.g., liquids, gases) within resonator vessels or chambers. For example, standing waves of an acoustic field can be generated and set up within a resonator containing a fluid medium. The acoustic fields can be described by three-dimensional scalar fields conforming to the driving conditions causing the fields, the geometry of the resonator, the physical nature of the fluid supporting the acoustic pressure oscillations of the field, and other factors.
One common way to achieve an acoustic field within a resonator is to attach acoustic drivers to an external surface of the resonator. The acoustic drivers are typically electrically-driven using acoustic drivers that convert some of the electrical energy provided to the drivers into acoustic energy. The energy conversion employs the transduction properties of the transducer devices in the acoustic drivers. For example, piezo-electric transducers (PZT) having material properties causing a mechanical change in the PZT corresponding to an applied voltage are often used as a building block of electrically-driven acoustic driver devices. Sensors such as hydrophones can be used to measure the acoustic pressure within a liquid, and theoretical and numerical (computer) models can be used to measure or predict the shape and nature of the acoustic field within a resonator chamber.
If the driving energy used to create the acoustic field within the resonator is of sufficient amplitude, and if other fluid and physical conditions permit, cavitation may take place at one or more locations within a liquid contained in an acoustic resonator. During cavitation, vapor bubbles, cavities, or other voids are created at certain locations at times within the liquid where the conditions (e.g., pressure) at said certain locations and times allow for cavitation to take place.
Under certain conditions, the acoustic action of a transducer and the resonance chamber may set up an acoustic field within the fluid in the chamber that is of sufficient strength and configuration to cause acoustic cavitation within a region of the resonance chamber. Specifically, under suitable conditions, acoustic cavitation of the fluid in the chamber may cause bubbles or acoustically-generated voids, as described above and known to those skilled in the art, to form within one or more regions of the chamber. The cavitation usually occurs at zones within the chamber that are subjected to the most intense (highest amplitude) acoustic fields therein.
Other ways have been known to cause acoustic cavitation in liquids and similar materials. For example, a high-intensity acoustic horn comprising a special metallic horn-shaped tool at one end that is driven by an electrical driver can be used to impart sufficient acoustic energy into a fluid so as to cause cavitation voids in a region of the fluid.
The detailed description below provides numerous embodiments and benefits of applying acoustical energy and cavitation to a suitable material in order to cause and sustain cavitation in the same.